The present embodiments relate to generating a voltage pulse with a pulse generator.
Marx generators generate transient pulse voltages of short duration and high amplitude.
Marx generators charge a large number of capacitors in parallel with direct voltage to the value of a stage voltage and then connect the capacitors suddenly in series. As the parallel-connected capacitors are being charged, the charging currents are added, and when subsequently series-connected, the voltages are added, as required, via the capacitors.
A charging voltage is provided, for example, via a transformer and an appropriately rated rectifier. The charge voltage charges a pulse capacitance via a charging resistor and/or a charging coil. The charging process generally occurs relatively slowly over a period in the range of several seconds. The voltage at the pulse capacitor follows an e-function and reaches its quasi-stationary final value after approximately 5τ. A spark gap is adjusted such that at the quasi-stationary final voltage value, the spark gap fails to break down. The spark gap can be brought to flashover after an arbitrarily selectable time period by suitable ignition devices. At this moment, the spark gap constitutes a closed switch. The temporal course of the pulse voltage emitted is determined via the component values of the generator and via the electrical values of the load.
With a single-stage pulse circuit, which may be called a cell, no higher voltage than the charging voltage can be achieved at the load. For the pulse voltages needed, a multi-stage arrangement of several cells in a Marx circuit is used in high-voltage installations.
DE 103 20 425 A1 discloses a Marx generator. The Marx generator has a number n of pulse capacitors. The pulse capacitors may be called stage capacitors. DE 103 20 425 A1 discloses a trigger/ignition device in the Marx generator including n stage capacitors (n is natural and greater than 1), an equal number of switches/spark gaps, and 2(n−1) charging branches. The spark gaps of the Marx generator operate in self-breakdown mode. The trigger/ignition device includes at least one pulse transformer connected to a pulse generator. In at least one of the charging branches of the Marx generator, an overvoltage, which is sufficient for self-breakdown, is generated in a time-determined manner for a short period at the adjacent spark gap. The charging branch with the associated stage capacitor bridges the spark gap, except at the output end. The output winding of the pulse transformer acts during the charging as a charging coil/inductivity. The input winding is connected to the pulse generator. The voltage pulse, which is generated with the pulse transformer upon ignition/triggering of the pulse generator, is added to the charge voltage of the associated stage capacitor and generates for a short period the overvoltage necessary for self-breakdown of the adjacent spark gap.
All n stage capacitors of the cells are charged simultaneously via the charging direct voltage. Coils can limit the charge current. The sparking distances of the spark gaps are chosen such that the paths fail to break down when the maximum charge voltage is reached. When all the pulse capacitors have been charged to their quasi-stationary final voltage value, ignition at the first spark gap takes place. At the next spark gap, a voltage that is now twice as high, namely twice the charge voltage, is applied so that this will also ignite. Within an extremely short time, all the spark gaps ignite in this manner, such that n times the stage voltage declines at the load.